Radiation is the highest energy on the electromagnetic spectrum. (The electromagnetic spectrum is a wide range of energies, normally the more dangerous energies are ultraviolet radiation, X-rays, and gamma rays.) Ionizing radiation is when radiation has high energy and removes electrons from atoms and molecules. Non-Ionizing radiation is when radiation has less energy. It doesn’t remove electrons from atoms and molecules.

Radiation damages your DNA cells (means you have a higher risk of cancer, and organ failure). It can also cause ARS (acute Radiation syndrome). ARS is also known as radiation sickness; it can happen when you're exposed to a high dose of radiation and most of your entire body has the radiation in it. It can also cause CRI (Cutaneous Radiation Injuries). CRI is when you get injuries on the outer part of your body like skin burns, it happens when exposed to large amounts of radiation.

Ionizing Radiation in the atmosphere can affect the growth of plants and animals in the environment if they are exposed to it. It can contaminate the air, water and other surfaces. It can also cause organisms to have genetic mutations. Living things can get radiation poisoning.

In a meltdown, the chain reaction is not controlled, and reactor fuel temperatures increase until they melt. In addition to the fuel rods melting, the heat passes to the water in the reactor; this generates high pressures. If the hot uranium contacts water, it can react to form hydrogen. The steam pressures and/or the explosion of the hydrogen can rupture the reactor vessel and allow radioactive vapors to escape. Sends out a cloud of radiation that will fall down onto the surrounding area, known as a plume zone. 

Radioactive materials in the plume from the nuclear power plant can settle and contaminate people who are outdoors, buildings, food, water, and livestock. Radioactive materials entering a person through breathing Radioactive materials can also get inside the body if people breathe it in or eat or drink something that is contaminated. People living close to the nuclear power plant who are exposed to radiation could experience long-term health effects such as cancer. (Yes, it is dangerous to a living organisms health/ welling being).